This invention relates generally to exhaust systems, and specifically to exhaust systems for marine and other limited-space environments, for controlling and disposing of engine exhaust gases while attenuating the engine noise associated with exhaust gases expelled from the engine.
Historically, society has gradually increased restrictions on the amount of noise which is tolerated from vehicles driven by internal combustion engines. Restrictions have been placed on automobile noise emissions. Restrictions have also been placed on aircraft noise emissions. More recently, restrictions have been imposed in some localities on boat noise emissions.
The difficulty with sound attenuation in the context of boats is that there is typically more limited room in a boat or boat engine compartment, thus precluding use of an expansive e.g. automobile-style muffler where the exhaust gases typically make two or more 180 degree turns inside the muffler. Existing designs of water craft typically do not provide adequate space, given the engine design contemplated for the water craft, to accommodate an automotive-style muffler of sufficient size to suitably control sound emissions from the engine.
A further complication is that consumers prefer increasingly larger size engines in marine vehicles, which emit greater volumes of exhaust gases, and are accompanied with greater levels of the sound which must be attenuated as the gases travel between the engine exhaust ports and the exhaust tip of the exhaust system.
Conventional high performance marine exhaust systems have routinely run the exhaust gases out the rear of the boat, with the only sound attenuation being whatever attenuation is incidentally developed by a spray of water injected into the exhaust pipe just behind the exhaust header.
Thus, there is a requirement for a sound-attenuating exhaust system, especially an exhaust system effective in marine applications, which is compact in size, effective in attenuating sound, and cost effective.
This invention relates generally to an in-line exhaust system which operates in an exhaust pipe generally sized to handle the exhaust gases, with conventional sound-attenuation treatment in a conventional sound attenuation cannister, from a respective size engine, whereby desired levels of sound attenuation can be accomplished while operating within, or substantially close to, the external dimensions of an exhaust pipe suitable for use with such engine while using conventional sound attenuation devices. Thus, the invention achieves sound attenuation while adding little or no space requirements in additional to the conduit requirements for conveying the exhaust gases to the rear of the boat for expulsion to ambient.
It is an object of the invention to provide a suitable sound attenuating exhaust system which utilizes an in-line sound attenuation design which continually passes the exhaust gases toward an exit tip of the exhaust pipe.
Another object is to provide an in-line sound-attenuating exhaust system wherein at least a first apertured baffle plate, having substantial gas-deflecting surface area, extends across the gas flow channel of an exhaust pipe at an oblique angle to the longitudinal axis of the exhaust pipe.
It is a further objective to provide a sound-attenuating exhaust system, and a baffle for use in such sound-attenuating exhaust system, wherein the baffle has multiple baffle plates, first and second such baffle plates having aperture configurations different and distinct from each other.
It is another objective to provide an exhaust system, and a baffle, including first, second, and third baffle plates, and wherein at least one such baffle plate defines a plate angle, relative to a longitudinal axis of such baffle, different from another such plate angle.
Yet another objective is to provide an exhaust system comprising an internally-carried baffle having a length of no more than 36 inches, wherein the exhaust system is effective to reduce sonic intensity by at least 3 decibels.
It is still another objective to provide an exhaust system, including an exhaust pipe and a baffle inside the exhaust pipe, wherein the baffle and exhaust pipe define a friction fit therebetween, and wherein force exerted on the exhaust receiving surface of the first, input baffle plate increases the intensity of the friction fit.
Still another objective is to provide an in-line sound-attenuating exhaust system wherein baffle plates, in combination with the internal surface of the exhaust pipe, define sound attenuation chambers having longitudinal cross-sections, and wherein no cross-section configuration represents more than 50 percent of the cross-sections in the baffle.
It is still another object of the invention to provide an in-line exhaust system wherein each baffle plate defines a different angle or angle pattern with a longitudinal axis of the baffle.
Still another object is to provide an in-line sound-attenuating exhaust system wherein first and second elliptical, apertured baffle plates are joined to each other and cross each other in a gas flow channel of an exhaust pipe.
Yet another object is to provide an in-line sound-attenuating exhaust system wherein at least first and second substantially planar baffle plates extend across substantially the full cross-section of the gas flow channel of the exhaust pipe, at oblique angles, spaced from each other and parallel to each other.
In a first family of embodiments, this invention comprehends in-line sound attenuating exhaust systems for use in combination with internal combustion engines. Such exhaust system comprises an exhaust pipe having first and second ends, and a length between the first and second ends, an inner surface, an outer surface, a gas flow channel, and a longitudinal axis. Such exhaust system further comprises a sound-attenuating baffle disposed in the exhaust pipe. The baffle comprises at least a first baffle plate extending across the gas flow channel at an oblique angle to the longitudinal axis of the exhaust pipe. The baffle plate has an exhaust receiving surface defining substantial gas-deflecting surface area, an exhaust discharging surface, and an array of apertures extending between the exhaust receiving surface and the exhaust discharging surface.
The baffle preferably includes a second baffle plate having a second array of apertures, the second baffle plate being joined to the first baffle plate, preferably in edge-to-edge relationship with the first plate, thus preferably forming an included angle with the first baffle plate, and extending across the gas flow channel at a second oblique angle to the longitudinal axis. The second oblique angle is preferably different from the first oblique angle, and can be a mirror image of the first oblique angle.
In some embodiments, the baffle further comprises a backwash valve secured over one of the baffle plates.
Where the baffle is comprised of first and second plates, the plates in some embodiments form a fixed included angle therebetween of about 100 degrees to about 130 degrees. Where more than two plates are used, the magnitude of the first plate angle with respect to the longitudinal axis is preferably different from the magnitude of the second plate angle and included angles between the plates are typically no more than 90 degrees.
In preferred embodiments, the magnitudes of the first and second plate angles with respect to the longitudinal axis cooperate with each other in attenuating different sonic frequencies of exhaust gases passing through the baffle.
In some embodiments, at least one of the first and second arrays of apertures comprises individual apertures each defining a like projected aperture area and wherein the apertures in the aperture configuration are uniformly spaced from each other.
In other embodiments, at least one of the first and second arrays of apertures comprises respective ones of the apertures in the given array which define different projected aperture areas and wherein the apertures in the aperture configurations are not uniformly spaced from each other.
Preferably, the first and second aperture configurations are different and complement each other in attenuating sonic energy in exhaust gases, and preferably in controlling back pressure exerted by the exhaust gases and passing through the baffle along the longitudinal axis.
In some embodiments, at least one of the aperture configurations comprises at least one of plural aperture sizes and plural aperture designs.
In preferred embodiments, the baffle plates are substantially planar.
In a second family of embodiments, the invention comprehends baffles used in exhaust systems of the invention, In preferred such baffles, the aperture configurations in the respective baffle plates are different and distinct from each other.
In preferred embodiments of the baffles having at least three baffle plates, optionally four or more baffle plates, and wherein each baffle plate defines, in edge view, a plate angle with the longitudinal axis, at least one plate angle is different from another such plate angle.
A backwash valve can be secured over one of the baffle plates, preferably a terminal one of the plates such as a tip plate.
In a third family of embodiments, the invention comprehends an in-line sound attenuating exhaust system for use in combination with an internal combustion engine. The sound attenuating exhaust system comprises an exhaust pipe having first and second ends, and a length between the first and second ends, an inner surface, an outer surface, a gas flow channel, and a longitudinal axis of the exhaust pipe; and a sound-attenuating baffle disposed in the exhaust pipe, the baffle comprising a first baffle plate having a first exhaust receiving surface, a first exhaust discharging surface, a first perimeter wall, and a first array of apertures extending between the first exhaust receiving surface and the first exhaust discharging surface, and a second baffle plate, joined to the first baffle plate, the second baffle plate having a second exhaust receiving surface, a second exhaust discharging surface, a second perimeter wall, and a second array of apertures extending between the second exhaust receiving surface and the second exhaust discharging surface. The first and second perimeter walls define a combined projected perimeter of the baffle along a common projection of the first and second perimeter walls, thereby to define a second longitudinal axis of the sound-attenuating baffle. The first and second arrays of apertures define respective first and second aperture configurations, different and distinct from each other.
In preferred embodiments, the sound-attenuating baffle is oriented in the pipe such that exhaust gases approach the second exhaust receiving surface after approaching the first exhaust receiving surface, and after passing through the first array of apertures.
In some embodiments, the sound-attenuating baffle is disposed adjacent an outlet end of the exhaust pipe.
In some embodiments, the first and second baffle plates define respective first and second different plate angles with the second longitudinal axis.
In preferred embodiments, the sound attenuating baffle has a length, taken along the second longitudinal axis, of no more than about 36 inches, and the exhaust system is effective to reduce sonic intensity of internal combustion engine exhaust passed therethrough by at least 3 decibels.
In attainment of such sound attenuation, and especially where the length of the baffle is so limited, the exhaust system can employ an imperforate outer wall of he exhaust pipe at the baffle location, a perforate inner wall, and an outer sound attenuation chamber between said outer and inner walls. The baffle plates have sufficient sound-deflection surface area, and are disposed at such angles with respect to gas flow through the baffle, as to deflect substantial portions of a gas, traversing the exhaust pipe, toward the outer chamber, as to both enhance mixing of gases traversing the exhaust pipe and to cause movement of such gases through the inner wall of the exhaust pipe into the outer sound-attenuation chamber.
In preferred embodiments, the baffle and exhaust pipe, in combination, define a friction fit between the inner surface of the exhaust pipe and the first and second perimeter walls of the baffle plates. Typically, the perimeter walls of the baffle plates are in surface-to-surface contact with the inner surface of the respective exhaust pipe along the full lengths of the perimeter walls so as to enhance frictional holding of the baffle and to limit the amount of gas which leaks past the plate at the perimeter wall.
The baffle is made from material having sufficient bending resilience, and the friction fit is cooperatively configured, such that force exerted on the exhaust receiving surface of the first e.g. input plate increases the intensity of the friction defined by the friction fit between the exhaust pipe and the baffle plate.
In the friction fit embodiments, the perimeter walls are preferably free from apertures thereby to enhance bending resistance and corresponding friction fit strength at the perimeter walls.
In preferred embodiments employing multiple baffle plates, each combination of adjacent facing baffle plates, in combination with a portion of the inner surface of the exhaust pipe, defines a sound-attenuation chamber having a maximum-area longitudinal cross-section and cross-section configuration, and no cross-section configuration represents more than 50 percent of such cross-sections in the baffle.
In some such embodiments, each sound-attenuation chamber defines a unique maximum-area longitudinal cross-section configuration such that each sound attenuation chamber preferentially attenuates a different range of sound frequencies.
Preferably, no pair of once-removed sound-attenuation chambers define the same cross-section configuration. As used herein, a once-removed sound-attenuation chamber has a single sound attenuation chamber longitudinally spaced between itself and a reference sound attenuation chamber.
A specific example of a preferred baffle has, in sequence, a first baffle plate defining a perpendicular angle with the longitudinal axis of the baffle, a second baffle plate defining a 45 degree angle with the longitudinal axis of the baffle, a third baffle plate defining a perpendicular angle with the longitudinal axis of the baffle, and a fourth baffle plate defining a 35 degree angle with the longitudinal axis of the baffle.
In another specific example of preferred baffles of the invention a first baffle plate defines, in sequence, a 75 degree angle with the longitudinal axis of the baffle, a second baffle plate defines a 65 degree angle with the longitudinal axis of the baffle, a third baffle plate defines a perpendicular angle with the longitudinal axis of the baffle, and a fourth baffle plate defines a 35 degree angle with the longitudinal axis of the baffle.
In some preferred baffles, each baffle plate defines on the respective exhaust-receiving surface, a unique angle or angle pattern with respect to the longitudinal axis of the baffle.
In a further family of embodiments, an in-line sound attenuating exhaust system for use in combination with an internal combustion engine comprises the exhaust pipe, and a baffle disposed in the exhaust pipe. The baffle comprises a first generally elliptical baffle plate having a first exhaust receiving surface, a first exhaust discharging surface, a first perimeter wall, and a first array of apertures extending between the first exhaust receiving surface and the first exhaust discharging surface, and a second generally elliptical baffle plate, joined to and crossing the first baffle plate at a single line of intersection extending across widths of the first and second baffle plates, the second baffle plate having a second exhaust receiving surface, a second exhaust discharging surface, a second perimeter wall, and a second array of apertures extending between the second exhaust receiving surface and the second exhaust discharging surface.
In preferred such embodiments, the line of intersection is preferably a straight line.
In some embodiments, the elliptical configurations of the first and second baffle plates are so designed in combination with the exhaust pipe and the line of intersection that the baffle is configured such that substantial portions of the perimeter walls engage the inner surface of the exhaust pipe, and such that the line of intersection extends at an angle across the longitudinal axis of the exhaust pipe, wherein the baffle plates extend across a cross-section of the gas flow channel in the exhaust pipe so as to substantially close off gas flow around the baffle plates at the perimeter walls and to define an entrance surface of the baffle defined in part by each of the first and second baffle plates and receiving initial baffle exposure to exhaust gases traversing the gas flow channel of the exhaust pipe.
An exit surface of the baffle is defined in part by discharging surfaces of each of the first and second baffle plates and receives the last baffle exposure to exhaust gases traversing the exhaust pipe. First and second enclosures on opposing sides of the line of intersection are each defined by portions of the first and second baffle plates in combination with a portion of the inner surface of the exhaust pipe. Exhaust gases traversing such exhaust pipe pass through a first set of apertures in the baffle plates at the entrance surface thus to enter the enclosures, and pass through a second different set of apertures in the baffle plates toward the exit surface thus to exit the enclosures and accordingly to exit the baffle.
In preferred such embodiments, the exhaust pipe comprises an imperforate outer wall, a perforate inner wall, and an outer sound attenuation chamber between the outer and inner walls. The baffle plates have sufficient sound-deflection surface area, and are disposed at such angles with respect to gas flow through the baffle, as to deflect substantial portions of a gas, traversing the exhaust pipe, toward the outer chamber, so as to both enhance mixing of gases traversing the exhaust pipe and cause movement of such gases through the inner wall of the exhaust pipe into the outer sound-attenuation chamber.
In other embodiments of the invention, the first and second baffle plates are substantially planar, the first and second baffle plates extend transversely across substantially a full width of the gas flow channel at oblique angles, the first and second baffle plates are oriented parallel to each other and are spaced from each other along the length of the exhaust pipe with sufficient generally open space therebetween to define a useful sound-attenuation chamber.
In such baffles the multiple baffle plates are preferably joined to each other by brackets extending between respective ones of the baffle plates whereby the baffle is a unitary assembly.